Problem with Stray Vertex Cleanup Algorithm
Posted: Mon Jun 24, 2013 7:19 pm
Hey guys,
In games, models can use vertex buffers that are shared among multiple input layouts. However, in Blender, you can only have one vertex buffer per mesh object, which kind of sucks because in games there may be only one vertex buffer with 50,000 vertices, but many input layouts that reference only 5,000 vertices or so at a time. So to get models into Blender I have to create new vertex buffers (based on what vertices are referenced by the index buffers), one per mesh object; otherwise, I would get a lot of stray points.
So this is my algorithm (example):
vertex buffer (6 vertices)
v0
v1
v2
v3
v4
v5
index buffer (6 indices)
0, 2, 5, 1, 3, 4
input layout #1 (mesh #1)
index buffer start: 0
index buffer elem: 3
input layout #2 (mesh #2)
index buffer start: 3
index buffer elem: 3
To get the model in Blender, without stray points, I mark used indices
input layout #1: vertices 0, 2, 5 used
input layout #2: vertices 1, 3, 4 used
Then I remap the indices:
input layout #1: vertices 0, 2, 5 used -> remapped to 0, 1, 2
input layout #2: vertices 1, 3, 4 used -> remapped to 0, 1, 2
And in Blender we are left with:
Mesh Object #1
Vertex Buffer: v0, v2, v5
Index Buffer: 0, 1, 2
Mesh Object #2
Vertex Buffer: v1, v3, v4
Index Buffer: 0, 1, 2
However, this is my problem:
Model looks great.
Weights are great.
UV DATA BECOMES SHIT THOUGH. Some UV end up being rotated. How bad it depends on the mesh. Overall I say 90% of UVs are correct. Some meshes have 0 bad UVs. Some meshes have only 1 or 2 bad UVs. Then there are some meshes where almost all UVs are shit.
I have looked at my algorithm and it looks great, but this rotate UV problem is driving me fucking bonkers
! Is there anything I'm forgetting about the remapping of vertex and index buffers that would cause rotated UVs?
This is a my index buffer remapping code. It takes an index buffer, and returns a map that maps old indices to a new indices.
Then the only thing needed to be done is save out new vertex buffers, which is pretty straightforward.
In games, models can use vertex buffers that are shared among multiple input layouts. However, in Blender, you can only have one vertex buffer per mesh object, which kind of sucks because in games there may be only one vertex buffer with 50,000 vertices, but many input layouts that reference only 5,000 vertices or so at a time. So to get models into Blender I have to create new vertex buffers (based on what vertices are referenced by the index buffers), one per mesh object; otherwise, I would get a lot of stray points.
So this is my algorithm (example):
vertex buffer (6 vertices)
v0
v1
v2
v3
v4
v5
index buffer (6 indices)
0, 2, 5, 1, 3, 4
input layout #1 (mesh #1)
index buffer start: 0
index buffer elem: 3
input layout #2 (mesh #2)
index buffer start: 3
index buffer elem: 3
To get the model in Blender, without stray points, I mark used indices
input layout #1: vertices 0, 2, 5 used
input layout #2: vertices 1, 3, 4 used
Then I remap the indices:
input layout #1: vertices 0, 2, 5 used -> remapped to 0, 1, 2
input layout #2: vertices 1, 3, 4 used -> remapped to 0, 1, 2
And in Blender we are left with:
Mesh Object #1
Vertex Buffer: v0, v2, v5
Index Buffer: 0, 1, 2
Mesh Object #2
Vertex Buffer: v1, v3, v4
Index Buffer: 0, 1, 2
However, this is my problem:
Model looks great.
Weights are great.
UV DATA BECOMES SHIT THOUGH. Some UV end up being rotated. How bad it depends on the mesh. Overall I say 90% of UVs are correct. Some meshes have 0 bad UVs. Some meshes have only 1 or 2 bad UVs. Then there are some meshes where almost all UVs are shit.
I have looked at my algorithm and it looks great, but this rotate UV problem is driving me fucking bonkers
! Is there anything I'm forgetting about the remapping of vertex and index buffers that would cause rotated UVs?This is a my index buffer remapping code. It takes an index buffer, and returns a map that maps old indices to a new indices.
Code: Select all
inline std::map<uint32, uint32> CreateZeroIndexedMap(const uint16* data, uint32 elem, uint32 start)
{
typedef std::set<uint16> set_type;
typedef std::map<uint32, uint32> map_type;
typedef std::map<uint32, uint32>::value_type value_type;
// mark used vertex indices
std::set<uint16> used;
for(uint32 i = 0; i < elem; i++)
if(data[start + i] != 0xFFFF) used.insert(data[start + i]);
// map old vertex index to new vertex index
uint32 curr_index = 0;
map_type retval;
for(set_type::iterator iter = used.begin(); iter != used.end(); iter++)
retval.insert(value_type(*iter, curr_index++));
return retval;
}
Code: Select all
// transform vertex buffer
for(auto iter = imap.begin(); iter != imap.end(); iter++)
{
// get indices
uint32 old_index = reference.vb_start + iter->first;
uint32 new_index = iter->second;
// copy position
vbnew.data[new_index].vx = vbuffer.data[old_index].vx;
vbnew.data[new_index].vy = vbuffer.data[old_index].vy;
vbnew.data[new_index].vz = vbuffer.data[old_index].vz;
// copy normal
vbnew.data[new_index].nx = vbuffer.data[old_index].nx;
vbnew.data[new_index].ny = vbuffer.data[old_index].ny;
vbnew.data[new_index].nz = vbuffer.data[old_index].nz;
// copy tangent
vbnew.data[new_index].tx = vbuffer.data[old_index].tx;
vbnew.data[new_index].ty = vbuffer.data[old_index].ty;
vbnew.data[new_index].tz = vbuffer.data[old_index].tz;
// copy binormal
vbnew.data[new_index].bx = vbuffer.data[old_index].bx;
vbnew.data[new_index].by = vbuffer.data[old_index].by;
vbnew.data[new_index].bz = vbuffer.data[old_index].bz;
// copy blend weights
vbnew.data[new_index].wv[0] = vbuffer.data[old_index].wv[0];
vbnew.data[new_index].wv[1] = vbuffer.data[old_index].wv[1];
vbnew.data[new_index].wv[2] = vbuffer.data[old_index].wv[2];
vbnew.data[new_index].wv[3] = vbuffer.data[old_index].wv[3];
vbnew.data[new_index].wv[4] = vbuffer.data[old_index].wv[4];
vbnew.data[new_index].wv[5] = vbuffer.data[old_index].wv[5];
vbnew.data[new_index].wv[6] = vbuffer.data[old_index].wv[6];
vbnew.data[new_index].wv[7] = vbuffer.data[old_index].wv[7];
// copy blend indices
vbnew.data[new_index].wi[0] = vbuffer.data[old_index].wi[0];
vbnew.data[new_index].wi[1] = vbuffer.data[old_index].wi[1];
vbnew.data[new_index].wi[2] = vbuffer.data[old_index].wi[2];
vbnew.data[new_index].wi[3] = vbuffer.data[old_index].wi[3];
vbnew.data[new_index].wi[4] = vbuffer.data[old_index].wi[4];
vbnew.data[new_index].wi[5] = vbuffer.data[old_index].wi[5];
vbnew.data[new_index].wi[6] = vbuffer.data[old_index].wi[6];
vbnew.data[new_index].wi[7] = vbuffer.data[old_index].wi[7];
// copy texture coordinates
for(uint32 i = 0; i < 8; i++) {
vbnew.data[new_index].uv[i][0] = vbuffer.data[old_index].uv[i][0];
vbnew.data[new_index].uv[i][1] = vbuffer.data[old_index].uv[i][1];
}
// copy vertex colors
for(uint32 i = 0; i < 8; i++) {
vbnew.data[new_index].color[i][0] = vbuffer.data[old_index].color[i][0];
vbnew.data[new_index].color[i][1] = vbuffer.data[old_index].color[i][1];
vbnew.data[new_index].color[i][2] = vbuffer.data[old_index].color[i][2];
vbnew.data[new_index].color[i][3] = vbuffer.data[old_index].color[i][3];
}
}
. I'm just kidding; I've been meaning to write a Noesis plugin for quite some time but I don't like bugging you or Chris when I have too many questions (like can I view vertex colors in Noesis, can I view UV maps in Noesis, can I view morphs in Noesis, does it support multiple UV channels, position channels, etc. etc.).